According to the state of a radio channel, transmit data is subject to error in a wireless communication system. The wireless communication system can control and recover the data error using an Automatic Repeat reQuest (ARQ) scheme or a Forward Error Correction (FEC) scheme.
A mobile station (MS) determines whether to employ the ARQ scheme in a registration procedure with its serving base station (BS) or in a service flow connection. When determining to use the ARQ scheme, the MS negotiates parameters required by the ARQ with the serving BS.
In negotiating the parameters required for the ARQ scheme, the serving BS and the MS determine ARQ_SYNC_LOSS_TIMEOUT for synchronization between the transmitter ARQ and the receiver ARQ.
The transmitter resets a timer which operates by the period ARQ_SYNC_LOSS_TIMEOUT upon every updating of ARQ_TX_WINDOW_START for ARQ synchronization with the receiver.
When ARQ_RX_WINDOW_START is updated or data valid in an ARQ RX window is received, the receiver resets the timer which operates by the period ARQ_SYNC_LOSS_TIMEOUT for ARQ synchronization with the transmitter.
When the driving time of the timer which operates by the period ARQ_SYNC_LOSS_TIMEOUT exceeds ARQ_SYNC_LOSS_TIMEOUT, the transmitter and the receiver reset the ARQ. For instance, the wireless communication system maintains ARQ synchronization of the transmitter and the receiver using ARQ_SYNC_LOSS_TIMEOUT as shown in FIG. 1.
FIG. 1 illustrates signal flows for ARQ reset in a conventional broadband wireless access system.
A transmitter 100 sends data received from an upper stage to a receiver 120 in step 101. In so doing, the transmitter 100 drives a first timer which operates by the period ARQ_SYNC_LOSS_TIMEOUT in step 103.
In step 105, the receiver 120, upon receiving the data without error from the transmitter 100, drives a second timer which operates by the period ARQ_SYNC_LOSS_TIMEOUT.
In step 107, the receiver 120 sends ARQ feedback information of the received data to the transmitter 100.
Upon receiving the ARQ feedback information of the data transmitted to the receiver 120, the transmitter 100 resets the first timer in step 109.
When the first timer expires, the transmitter 100 and the receiver 120 transmit and receive ARQ reset messages in step 111. In so doing, the transmitter 100 and the receiver 120 reset the ARQ.
When the first timer expires, the first timer is reset to drive continuously in step 113.
When the first timer expires again, the transmitter 100 and the receiver 120 transmit and receive ARQ reset messages in step 115. In so doing, the transmitter 100 and the receiver 120 reset the ARQ.
In the ARQ as discussed above, the transmitter and the receiver operate the timer which operates by the period ARQ_SYNC_LOSS_TIMEOUT to keep the ARQ synchronized. When the timer expires, the transmitter and the receiver recognize that the ARQ is out-of-synchronization and reset the ARQ.
However, since the timer continues to operate after the ARQ reset, the ARQ reset is repeated even though the ARQ window is empty.